This research is concerned with the ontogeny of ingestive behavior in rats. It will identify, describe and analyze: (1) the sensory, especially olfactory stimuli which elicit suckling in rats; (2) the ontogeny of thirst mechanisms including the experiences which control their normal expression; (3) the experiences necessary to maintain suckling; (4) the changing contributions of maternal and nutritional incentives in maintaining instrumental behavior during the nursing period, and the neurochemical mediators of memory in neonatal rats; (5) an additional aim of the proposed research is to extend our analyses to the awake, behaviorally competent albino rat and to the wood rat (Neotoma Lepida Lepida) to ascertain the generality of our findings derived from the behavior of albino neonates on their anesthetized mothers.